The purpose of this application is to define a program of research and study in which Dr. Kevin Gingrich can expand both his current interest in basic research and his skills in experimental laboratory techniques. A training program has been designed that will broaden Dr. Gingrich's theoretical background in cellular and molecular physiology, and additionally will provide him with extensive experimental experience in the measurement and analysis of ion channel currents in heart and other cells. These techniques are basic tools that are needed to probe the molecular basis of ion channel function and modulation by drugs. This training program will provide Dr. Gingrich with the background and technical skills to become an independent physician investigator in the field of molecular and cellular physiology. The overall program is scheduled for five years with two distinct phases: I and II. Phase I consists of basic research training in cellular and molecular electrophysiologic techniques to include both whole cell and single channel methods necessary for the study of ion channels in heart and other cells. Training will take place in the laboratory of his sponsor, Dr. Robert Kass, and will build on earlier training in the measurement and analysis of single channel currents in heart. Concurrently, Dr. Gingrich will audit relevant courses and follow a general training scheme under the guidance of Dr. Kass. Phase II of the program proposes an investigation of the molecular mechanisms involved in blockade of cardiac sodium channels by tertiary and quaternary amines. This class of drug includes clinically useful local anesthetics and anti-arrhythmics. In preliminary work, Dr. Gingrich has shown that a permanently charged derivative of lidocaine (QX-314) induces a novel type of blockade that is 'polarized' in nature. The hypothesis to be tested is that a fundamental component of polarized block results from the interaction of the blocker with the spatial constraints of the pore near the drug receptor. This will be investigated by examining the blockade induced by agents related to QX-314 that differ in their spatial qualities. This research will provide insight into the molecular mechanisms by which local anesthetics and anti-arrhythmics interact with sodium channels and may well be key to understanding and treating disorders of electrical conduction in the heart.